Microchipping dramatically increases the probability of lost cats being reunited with their owners. The brief procedural discomfort is far outweighed by the welfare benefit of preventing prolonged separation or euthanasia.
Lost cats without identification face prolonged welfare harm: days or weeks as strays exposed to traffic, predators, and weather, followed potentially by euthanasia if not claimed from shelters within holding periods. Microchipped cats that enter shelters can be returned immediately to their owners, eliminating this suffering entirely in most cases. The procedural welfare cost — seconds of discomfort during injection — is trivially small compared to the potential welfare benefit of preventing extended homelessness or death. Database registration is as important as the chip itself: a microchipped cat whose owner has moved or changed contact details cannot be reunited. Annual database verification ensures the system works when needed.